Power tools of all types use chucks to hold other tools in place which are to be driven. The tools may be large machine tools which are used in production machine environments, or may be small hand held drills into which drill bits of varying sizes are placed for driving. The most common tool which uses a chuck is a hand held drill, and for demonstrative purposes, will be used herein.
Drills commonly in use incorporate a motor which turns a shaft. A chuck is attached to the end of the shaft, into which a tool of the desired size is inserted and held. The combination is either called a drill motor and drill, or a drill and drill bit. In the former case, the drill motor provides rotation, with the drill being the tool which is rotated to produce a hole of a desired size in a material. In the latter case, which is usually associated with smaller, hand held drills, the drill is the device which provides the rotation, while the drill bit is the tool which actually produces the hole. The latter terminology will be used consistently herein.
The drill bit is mated to the drill by means of a chuck. As stated before, tools of all kinds use chucks, however, the chucks in common use are substantially similar. The chuck will commonly have three or four jaws which are relatively long and narrow, and are displaced angularly from the chuck body. The angular displacement allows for drill bits of varying diameters to be inserted therein, with a large diameter bit received when the jaws are retracted, and a smaller bit when the jaws are displaced.
Displacement and retraction of the jaws is accomplished by means of a threaded collar which surrounds the jaws. Grooves are present on the upper end and outside surface of the jaws so as to interact with the threaded collo. Rotation of the ring at a different velocity than the tool or drill shaft on which the jaws are located results in the displacement or retraction of the jaws due to the threaded interaction between the collar and the jaws.
As most commonly used in the prior art, displacement and retraction of the jaws is accomplished by manual means. A key having gear teeth cut therein is mated with gear teeth cut within the threaded ring so as to allow for the threaded ring to be rotated about the jaws. As the ring rotates about the jaws, the jaws are displaced or retracted, according to the direction of the rotation. As the jaws are displaced against the dril bit, torque is increased through the key to hold the jaws tight against the bit.
Chucks presently in widespread use then are actuated by rotating the threaded ring or collar at a different velocity than the jaws, with displacement or retraction dictated by the direction of rotation. Accordingly, it has long been recognized by persons using such tools as power drills that "power chucking" can be accomplished by manually holding the threaded ring or collar, or the cylinder which is attached thereto, while actuating the drill. In addition to being dangerous, manual pressure is generally insufficient to fully secure the drill bit within the chuck, and cannot be used to release the bit from the chuck. The chuck key must be resorted for releasing or finally securing the bit.
The prior art reveals various devices which aid the manual holding of the threaded ring or collar to allow for the complete tightening and releasing of the drill bit within the chuck when used with a reversible drill. These devices generally incorporate the manual method outlined above, but improve on same by providing a sliding collar or cylinder or similar device having lugs or teeth on one surface thereof which may be displaced and inserted into detentes or other voids on the drill so as to mate therewith. In essence, they provide a more positive method of manually securing the threaded ring or collar so that the torque of the drill can be used to fully tighten the chuck against the drill bit, as well as to loosen the chuck to remove the bit.
The devices found in the prior art are awkward to use, do not adequately deal with inertia when the chuck becomes fully tightened against the bit, and have not found widespread acceptance. For example, when a relatively small bit is initially inserted into the chuck, it is frequently necessary to hold the bit concentric with the shaft so that it does not lodge between the jaws in an improper fashion. At the same time it is necessary to hold the actuation collar or cylinder of the keyless chuck, while still at the same time manually actuating the switch of the drill's motor. Since very few operators have more than two hands available, it is very difficult to perform all three of these functions simultaneously as required by the keyless chucks found in the prior art. Further, these devices disengage the collar or cylinder by the torque of the motor and inertia when the jaws fully tighten against the drill bit. Inertia and the torque of the drill motor force the teeth or lugs out of the detentes or voids into which they are mated when the chuck is fully tightened. This design causes significantly wear on the lugs and detents, and is dangerous in its method for forcing the collar or cylinder out while it is being manually held.